Synthesis of a Heterometallic Trinuclear Cluster Containing Ruthenium and Cobalt and Its Reactivity with Internal Alkynes

A heterometallic tetrahydrido cluster composed by ruthenium
and
cobalt, (Cp*Ru)2(Cp*Co)­(μ-H)3(μ3-H) (1) (Cp* = η5-C5Me5), was exclusively synthesized by the reaction of Cp*Ru­(μ-H)4RuCp* with (Cp*CoCl)2 in the presence of LiBEt3H. X-ray diffraction and VT-NMR studies showed that 1 has a similar structure to the Ir and Rh analogues in terms
of the positions of the hydrido ligands, but the size of the trinuclear
site is considerably smaller than that of the iridium analogue because
of the smaller covalent radius of cobalt. Like the iridium analogue,
complex 1 reacted with internal alkynes to yield an equilibrated
mixture of perpendicularly coordinated alkyne complexes. However,
the structure of the major isomer was different from that of the iridium
analogue: the alkyne ligand on the Ru2Co core was preferentially
coordinated to one of the Ru–Co bonds.